engleski

Self-consistent field low rank perturbation method

The LRP-method is applied to the generalized perturbed eigenvalue equation, where the solution of the reference unperturbed equation is known. This method is generalized to the SCF approach. A simple case of rank one perturbation is considered. It is shown that the operation count required to perform a single SCF iteration is of the order O(n2), where n is the order of the matrices considered. This operation count is essentially independent of the magnitude of perturbation. In addition, the number of SCF iterations increases very slowly with the magnitude of the perturbation. The SCF LRP method can be applied to those problems where the rank of the perturbation is relatively small. In particular, it can be applied to localized perturbations, where only a few perturbation matrix elements are nonzero. Such are, for example, substitution of an atom in a molecule by a heteroatom, formation or breaking of a chemical bond, etc.

low rank perturbation ; SCF method ; generalized eigenvalue equation

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